Polynucleotide and protein involved in synaptogenesis variants thereof and their therapeutic and diagnostic uses

ABSTRACT

The invention concerns identification of human genes coding for a protein involved in synaptogenesis and whereof the mutation is associated in humans with the development of neurological diseases and/or predisposition to developing mental disorders or psychiatric diseases such as autism and asparagus syndrome. More particularly, the invention concerns a protein belonging to the family of human neuroligins (HNL&#39;s) and more particularly the HNL4X protein and its functional homologue HNL4Y encoded by a Y chromosome gene. The invention also concerns polynucleotides coding for the HNL4X and HNL4Y proteins mutated or not and mutated HNL3 proteins, the cellular expression vectors comprising the nucleic acid sequences expressing HNL3, HNL4X, HNL4Y mutated or not, and the polyclonal or monoclonal antibodies capable of being fixed on one of said peptides and/or polynucleotides mentioned above. The invention further concerns the use of polypeptides, polynucleotides, a vector, a host cell, and/or an antibody as defined above for preparing a composition for use in the treatment of a mental or neurological disease such as autism, asparagus syndrome, schizophrenia or the ADHD syndrome.

CONTEXT OF THE INVENTION

a) Field of the Invention

The present invention relates to the identification of a human gene encoding a protein involved in synapto-genesis and of its murine orthologs, the mutation of which is associated in humans with the development of neurological diseases and/or with a predisposition to the development of mental disorders or psychiatric diseases such as autism and Asperger syndrome.

The invention also relates to the diagnostic and therapeutic uses associated with identifying the gene and its mutations.

The invention also relates to the diagnostic and therapeutic uses associated with identifying the involvement of a defect in a protein of the neuroligin family in the development of mental disorders or psychiatric diseases such as autism and Asperger syndrome.

b) Brief Description of the Prior Art

Autism is a disease which affects around one child in 1000 and mainly boys (from 4 to 23 boys to one girl according to the selected clinical criteria). The clinical symptoms of autism are described in the DSM-IV-TR™ manual (Diagnostic and statistical manual of mental disorders, 2000, pages 70-75).

The molecular bases of autism are currently unknown. Studies have already suggested the existence of a genetic component in autism. Based on linkage analysis results, Philippe et al. (Human Molecular Genetics, 1999, 8:805-812) describes 11 chromosomal regions which may be involved in the development of autism, among which is a region of chromosome Xp. In addition, Thomas et al. (Hum. Genet., 1999, 104:43-48) describes deletions of the short arm of the X chromosome in patients suffering from autism, and Milunsky et al. (Clin. Genet., 1999, 55:455-460) describes deletions in Xp22 in patients suffering from schizophrenia and suggests, more precisely, the involvement of a deletion in Xp22.3 in the development of this psychiatric disease. However, neither the gene involved in the disease nor the nature of the mutation are mentioned.

The neuroligins (HNLs) are cell adhesion proteins which can trigger, by themselves, synaptogenesis, i.e. the formation of synapses (Scheiffele et al., Cell, 2000, 101:657-669). The neuroligins NL1, NL2 and NL3 were originally cloned in rats (Ichtchenko et al., Cell., 1995, 81(3):435-43; Ichtchenko et al., J. Biol. Chem., 1996, 271(5) :2676-82). The neuroligins HNL1 and HNL2 are located on autosomes (3q26 and 17p13). These genes are targets for susceptibility to psychiatric diseases and several protein variations in HNL2 have been demonstrated by the inventors in autistic patients (R734H, G754R, A755V). A protein HNL4X (human neuro-ligin-4) has been described by Bollinger et al. (Bio-chem. J., 2001, 356:581-588), without any genomic description or related biological function. In addition, the LOCUSLINK™ database (http://www.ncbi.nim.nih.gov) of Sep. 13, 2001 provides, under the accession numbers KIAA1260 and KIAA0951, incomplete sequences of a neuroligin gene, the function of which is also unknown. All neuroligins have an extracellular domain homologous with acetylcholine esterase (ACHE). Neuroligins interact with β-neurexins, at the level of this extracellular component (Ichtchenko et al., Cell., 1995, 81(3):435-43). This interaction can be modulated by ACHE itself (Grifman et al., Proc. Natl. Acad. Sci. USA, 1998, 95(23) :13935-40). At the cytoplasmic level, neuroligins interact with several proteins containing PDZ domains (Irie et al., Sciences, 1997, 277(5331):1511-5; Hirao et al., J. Biol. Chem. 1998, 273(33), 21105-10; Kurschner et al., Mol. Cell Neurosci., 1999, 11(3):161-72; Bolliger et al., Biochem J., 2001, 356:581-8; Toyooka et al., J Neurochem., 2002, 83(4):797-806). Among these proteins, are the proteins of the DLG1-5 family (3q29, 11q13, Xq13.1, 17p13.1 and 10q22.3), the S-SCAM protein (7q21.11), the proteins of the CIPP family (MPDZ, 9p23 and INADL, 1p31) and the CASK protein (Xp11).

In view of the above, it is clear that knowledge of the molecular bases of autism, and most particularly of the gene involved in the disease, is greatly desired in order to make it possible to develop novel therapeutic approaches, novel medicinal products and diagnostic tests.

A need also exists concerning identification of the biological function of neuroligins and also identification of the nucleic acid and protein sequence of neuroligins, in particular that of HNL3 and HNL4X.

The present invention satisfies these needs and other needs, as will be apparent to those skilled in the art upon reading the present description of the invention.

SUMMARY OF THE INVENTION

The present invention relates to the identification of human genes and of their murine ortholog encoding a protein involved in synaptogenesis, the mutation of which is associated, in humans, with the development of neurological diseases and/or with a predisposition to the development of mental disorders or psychiatric diseases such as autism and Asperger syndrome.

More particularly, a subject of the present invention is an isolated or purified polynucleotide encoding a polypeptide involved, in its wild-type form, in synaptogenesis. The polynucleotide of the present invention is characterized in that at least one mutation in the nucleic acid sequence of said polynucleotide is associated with the development of neurological diseases and/or with a predisposition to the development of mental disorders or psychiatric diseases.

Preferably, the present invention relates to a polynucleotide encoding a protein belonging to the family of human neuroligins (HNLs), and more particularly the HNL4X protein (previously called HNL4) and its functional homolog HNL4Y (previously called HNL5) encoded by a gene on the Y chromosome.

The present invention also relates to a polynucleotide encoding the mouse protein MNL4, which is the orthologs of the HNL4X and HNL4Y proteins.

According to another subject, the present invention is directed toward an isolated or purified polypeptide, characterized in that it is encoded by a polynucleotide as defined above. More particularly, the polypeptide according to the present invention is characterized in that it is involved in synaptogenesis, and in that the presence of at least one mutation in the amino acid sequence of said polypeptide is associated with a predisposition to the development of mental disorders or psychiatric diseases.

According to another subject, the present invention proposes a method for detecting biochemical disorders which alter synapse formation, and/or a predisposition to the development of psychiatric pathologies and/or a mental disease, comprising at least one of the following steps:

-   -   detecting a mutation in the sequence of a polynucleotide as         defined above, in the sequence of a fragment of said         polynucleotide or in the sequence of a messenger RNA of said         polynucleotide;     -   detecting the presence of a polypeptide as defined above;     -   detecting a mutation in a polypeptide as defined above;     -   measuring the activity of a polypeptide as defined above or the         interaction thereof with one of its protein partners.

Another object of the invention is to provide a kit for detecting biochemical disorders which alter synapse formation, and/or a predisposition to the development of psychiatric pathologies and/or a mental disease, and/or for diagnosing a mental disease, the kit comprising at least one of the elements chosen from the group consisting of: a probe, an antibody, a reagent and a solid support for:

-   -   i) detecting a mutation in the sequence of a polynucleotide as         defined above, in the sequence of a fragment of said         polynucleotide or in the sequence of a messenger RNA of said         polynucleotide; and/or     -   ii) measuring the biological activity of a polypeptide as         defined above or the interaction thereof with one of its protein         partners.

The invention also relates to the use of a nonmutated polynucleotide encoding a protein involved, in its wild-type form, in synaptogenesis, for treating or preventing biochemical pathologies or mental diseases.

The invention also relates to the use of a nonmutated polypeptide involved, in its wild-type form, in synaptogenesis, for treating or preventing biochemical pathologies or mental diseases.

The present invention also proposes a method for sorting molecules which makes it possible to modulate the biological activity of the polypeptide encoded by the polynucleotide defined above or the biological activity of the polypeptide defined above, comprising:

-   -   a) bringing said polypeptide or a recombinant cell containing it         into contact with a molecule capable of modulating its         biological activity;     -   b) measuring the biological activity of said polypeptide or its         interaction with one of its protein partners; and     -   c) evaluating the activity measured in step b) relative to a         measurement of the biological activity of said polypeptide in         the absence of said molecule.

Another subject of the present invention is directed. toward a method for treating a mental or neurological disease, comprising the insertion into at least one portion of the cells from an affected patient of a polynucleotide encoding a polypeptide as defined above.

The present invention also proposes a method for transforming stem cells from a patient exhibiting a mutation of a gene encoding a protein involved in synaptogenesis, characterized by

-   -   a) the use of stem cells from. said patient;     -   b) the insertion into the genome of said stem cells of a         polynucleotide as defined above; and     -   c) the reimplantation into the patient of cells transformed         according to step b).

The invention also relates to a cloning or expression vector comprising one of the polynucleotides of the invention or a fragment thereof; a host cell containing a polynucleotide and/or a vector according to the invention; or purified monoclonal or polyclonal antibodies which recognize specifically at least one of the polynucleotides of the invention and/or at least one of the polypeptides of the invention.

The invention is also directed toward a composition containing at least one element chosen from the group consisting of a) a polypeptide, b) a polynucleotide, c) a vector, d) a host cell and e) an antibody, and a pharmaceutically acceptable vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the region of chromosome Xp22.3 containing the HNL4X gene.

FIG. 2 shows a protein alignment for human neuroligins.

FIG. 3 is a diagram which shows the protein architecture of the synapse with the location and the known partners of neuroligins.

FIGS. 4A and 4B represent a diagram which shows the chromosomal location and the evolution of the HNL4X and HNL4Y genes.

FIG. 5 is a diagram which shows the genomic structure of the human neuroligin genes.

FIGS. 6A and 6B show the result of SSCP (single strand conformational polymorphism) analysis of a mutation of the gene encoding the HNL4X protein and also the sequence of this mutation.

FIG. 7 is a diagram which shows the location of the HNL4X protein and the effects of the mutation on HNL4X.

FIG. 8A represents the genomic sequence (SEQ ID NO:1) of the wild-type (nonmutated) human HNL4X gene.

FIG. 8B represents the nucleic acid sequence (SEQ ID NO:16) of exon 1 of FIG. 8A.

FIG. 9 represents the complementary DNA sequence (SEQ ID NO:2) of the wild-type (nonmutated) human HNL4X gene.

FIG. 10 represents the amino acid sequence (SEQ ID NO:3) of the wild-type (nonmutated) human HNL4X protein.

FIG. 11A represents the genomic sequence (SEQ ID NO:4) of the human HNL4Y gene.

FIG. 11B represents the nucleic acid sequence (SEQ ID NO:17) of exon 1 of FIG 11A.

FIG. 12 represents the complementary DNA (cDNA) sequence (SEQ ID NO:5) of the wild-type human HNL4Y gene.

FIG. 13 represents the amino acid sequence (SEQ ID NO:6) of the wild-type human HNL4Y protein.

FIG. 14 represents the complementary DNA (cDNA) sequence (SEQ ID NO:7) of an alternative transcript of the wild-type human HNL4Y gene.

FIG. 15 represents the amino acid sequence (SEQ ID NO:8) corresponding to the alternative sequence of FIG. 14.

FIG. 16 represents the amino acid sequence (SEQ ID NO:9) of the mutated human HNL4X protein.

FIG. 17 shows the chromosomal location of the HNL3, HNL4X and HNL4Y genes and the pedigree of a family exhibiting a mutation in HNL4X in an autistic boy and a boy suffering from Asperger syndrome.

FIG. 18 is a diagram which shows the conservation of the HNL3 mutations.

FIG. 19A shows the nucleic acid sequence of the cDNA of MNL4 (SEQ ID NO:62) (orthologs of HNL4X and HNL4Y).

FIG. 19B represents the amino acid sequence of the MNL4 protein (SEQ ID NO:63).

FIG. 20 is a diagram which shows the genomic structure of the HNL1, HNL2 and HNL3 genes, and also the location of the mutations observed in HNL3.

FIG. 21 is a diagram which shows the genomic structure of HNL4X and HNL4Y.

FIG. 22 shows a portion of the amino acid sequence (SEQ ID NO:10) of the HNL3 protein mutated at position 451.

FIG. 23 shows another portion of the amino acid sequence (SEQ ID NO:11) of the HNL3 protein mutated at position 796.

FIG. 24 represents the complementary DNA (cDNA) sequence (SEQ ID NO:12) of the wild-type HNL3 transcript.

FIG. 25 represents the complementary DNA (cDNA) sequence (SEQ ID NO:13) of the mutated HNL3 transcript.

FIG. 26 represents the amino acid sequence (SEQ ID NO:14) of the wild-type human HNL3 protein.

FIG. 27 represents the amino acid sequence (SEQ ID NO:15) of the mutated human HNL3 protein.

DETAILED DESCRIPTION OF THE INVENTION

The originality of the present invention relates to the identification of the genomic sequence of the HNL4X gene located at Xp22.3 and of a functional homolog HNL4Y placed on the Y chromosome, located at Yq11.22, and also their murine orthologs MNL4.

The invention also relates to the identification of the involvement of the proteins of synaptogenesis, in particular HNL3 and HNL4, in the development of mental disorders or psychiatric diseases such as autism.

1. Polypeptide and Polynucleotide

According to a first aspect, the present invention is directed toward an isolated or purified polypeptide which, in its wild-type (i.e. nonmutated) form, is involved in synaptogenesis, in which at least one mutation in the amino acid sequence is associated with the development of neurological diseases and/or with a predisposition to the development of mental disorders or psychiatric diseases.

The expression “mental disorders or psychiatric diseases” is intended to mean diseases such as autism, Asperger syndrome, schizophrenia and ADHD (attention deficit hyperactivity disorder) syndrome.

Preferably, the polypeptide consists of a cell adhesion protein, more preferably of a protein belonging to the human neuroligin family, and even more preferably the polyeptide consists of the HNL3 protein, HNL4X or the HNL4Y protein. Advantageously, when the polypeptide is HNL3, it comprises an amino acid sequence according to SEQ ID NO:14 and sequences of at least 20, of at least 50 and of at least 100 consecutive amino acids or more derived from SEQ ID NO:14. When the polypeptide of the invention is HNL4X or the HNL4Y protein, it comprises a sequence chosen from the group consisting of: SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO:8 and the sequences of at least 20, of at least 50 and of at least 100 consecutive amino acids or more derived from SEQ ID NO:3, SEQ ID NO:6 or SEQ ID NO:8.

The invention also relates to the “mutated” polypeptides and the polypeptides “derived” from the wild-type protein, preferably a neuroligin such as HNL3, HNL4X or HNL4Y.

The term “polypeptide derived” from a wild-type protein or “variant” of a wild-type protein is intended to mean all peptides which have a peptide sequence substantially identical, at least in part, to the peptide sequence of the wild-type protein. They may, for example, be chemically modified polypeptides having a peptide sequence 100% identical to a portion of the wild-type protein. They may also be hybrid polypeptides having a first portion 100% identical to a first portion of the wild-type protein and a second portion in no way/partially identical to a second portion of the wild-type protein. They may also be polypeptides having complete/partial homology with a portion of the wild-type protein.

The term “mutated” polypeptides derived from a wild-type protein is intended to mean all peptides which have been obtained following modification of said wild-type protein, whether this is modification by addition, deletion or substitution of one or more of the amino acids of the wild-type protein. It may also be a modification introduced by the addition of carbon chains attached to at least one of the amino acids of the wild-type protein or to at least one of the amino acids of the peptides for which there exists a substitution or a modification of one of the amino acids compared to the wild-type protein. More particularly, the present invention covers the peptides which derive from the human protein HNL3, HNL4X or HNL4Y.

According to a preferred embodiment, and when the polypeptide is a mutated HNL3 according to the present invention, it has SEQ ID NO:10, SEQ ID NO:11or SEQ ID NO:15, and a sequence of at least 20, of at least 50 and of at least 100 consecutive amino acids or more derived from SEQ ID NO:10, SEQ ID NO:11 or SEQ ID NO:15. When the polypeptide is a mutated HNL4X or a mutated HNL4Y according to the present invention, it has SEQ ID NO:9 or a sequence of at least 20, of at least 50 and of at least 100 consecutive amino acids or more derived from SEQ ID. NO:9.

The invention is also directed toward the polypeptides (and the fragments thereof) which are encoded by the nucleotide sequences mentioned hereinafter.

In the context of the present invention, the term “polypeptide” is defined as being any peptide or protein comprising at least two amino acids linked by a modified or unmodified peptide bond. The term “polypeptide” refers to short-chain molecules such as peptides, oligopeptides or oligomers or to long-chain molecules such as proteins. A polypeptide according to the present invention can comprise modified amino acids. Thus, the polypeptide of the present invention can also be modified by a natural process such as post-transcriptional modifications or by a chemical process. Some examples of these modifications are: acetylation, acylation, ADP-ribosylation, amidation, covalent bonding with flavine, covalent bonding with a heme, covalent bonding with a nucleotide or a nucleotide derivative, bonding with a lipid or a lipid derivative, covalent bonding with a phosphotidylinositol, cross-linking, cyclization, disulfide bond formation, demethylation, cysteine molecule formation, pyroglutamate formation, formylation, gamma-carboxylation, hydroxylation, iodination, methylation, oxidation, phosphorylation, racemization, hydroxylation, etc. Thus, any modification of the polypeptide which does not have the effect of eliminating the biochemical characteristics of the polypeptide of origin, i.e. the ability to form functional synapses, is covered within the scope of the present invention.

According to a related aspect, the invention is directed toward an isolated or purified polynucleotide encoding a polypeptide as defined above, and more particularly an isolated or purified polynucleotide encoding a polypeptide involved in synaptogenesis, in which at least one mutation of this polypeptide is associated with the development of neurological diseases and/or with a predisposition to the development of mental diseases or psychiatric diseases.

The term “isolated or purified” is intended to mean the molecules which have been altered, by man, from their natural state, i.e., if such a molecule exists naturally, it has been changed and/or removed from its initial environment. For example, a polynucleotide or a polypeptide naturally present in a living organism is not “isolated”. However, the same polynucleotide or polypeptide, when separated from its normal environment and/or obtained by cloning, amplification and/or by chemical synthesis, is considered according to the present invention as being “isolated”. Moreover, a polynucleotide or polynucleotide which is introduced into an organism by transformation or genetic manipulation or by any other method of recombination is “isolated” even if it is present in said organism.

The term “polynucleotide” is intended to mean any DNA or RNA molecule or sequence having two nucleotides or more, including the nucleic acid sequences encoding an entire gene. The term “polynucleotide” encompasses all nucleic acid molecules which are in the natural or artificial state. This includes DNA molecules, RNA molecules, cDNAs, expressed sequences (ESTs), artificial sequences and all the fragments thereof. It goes without saying that the “derived”, “variant” and “mutated” definitions also apply to the polynucleotides according to the present invention. Any polynucleotide which has been chemically, enzymatically or metabolically modified but which has conserved the biochemical properties of the polypeptide of origin, i.e. which has conserved its ability to form functional synapses, is included in the scope of the present invention.

According to a preferred embodiment, when the polynucleotide according to the invention encodes an HNL3 protein or a fragment of this protein, the latter advantageously comprisses SEQ ID NO: 14. Preferably, the polynucleotide comprises a sequence chosen from the group consisting of : SEQ ID NO: 12 and the sequences of at least 20, of at least 50 and of at least 100 consecutive nucleotides or more derived from SEQ ID NO: 12.

According to a preferred embodiment, when the polynucleotide according to the invention encodes an HNL4X or HNL4Y protein or a fragment of this protein, the latter advantageously comprises SEQ ID NO:3, SEQ ID NO:6 or SEQ ID NO:8. Preferably, the polynucleotide comprises a sequence chosen from the group consisting of: SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:16, SEQ ID NO:17 and the sequences of at least 20, of at least 50 and of at least 100 consecutive nucleotides or more derived from these sequences.

According to another embodiment, the polynucleotide encodes a nonfunctional mutated protein. Preferably, the polynucleotide encodes a mutated HNL3 or mutated HNL4X protein. When the protein is HNL4X, the polynucleotide is mutated such that the mutation causes early termination of the protein. More preferably, the polynucleotide of the invention comprises SEQ ID NO:1 and the mutation is an insertion of a thymine at position 1186, from position 465 of FIG. 9 (ORF). This mutation causes the production of a defective protein lacking its transmembrane portion since this mutation causes early termination of the protein (D396stop). When the mutated protein is HNL3, the mutation causes a modification of the protein sequence such as an amino acid substitution at position 451 and/or 796 of FIG. 18 or 21. More particularly, the mutation produced at position 451 consists of the substitution of an arginine with a cysteine, while the mutation produced at position 796 consists of the substitution of an asparagine with a serine. This amino acid, arginine R451, is located in the acetylcholine esterase domain of the neuroligins and is extremely conserved in all the neuroligins sequenced to date and in fish, bird and reptile acetylcholine esterases (FIGS. 6A and 6B).

The polypeptides and polynucleotides according to the present invention can be prepared by any suitable method. They can in particular be obtained by chemical synthesis, but it is also possible to obtain them biologically, using in particular various vectors in suitable cell cultures, as will be described hereinafter. The peptides according to the present invention can be in deglycosylated or glycosylated form, if this is necessary. Those with knowledge in the field of the invention will be able to obtain various polynucleotides/polypeptides and will also be able to determine which, among the polynucleotides/polypeptides obtained, are those which have an appropriate biological activity.

2. Vector, Antibody and Cell

According to another aspect, the invention relates to any vector (cloning and/or expression vector) and any cellular host (procaryotic or eukaryotic) transformed with such a vector, and comprising the regulatory elements for expression of the nucleotide sequence encoding a peptide according to the invention.

According to another aspect, a subject of the invention is a method for preparing a peptide of the invention, by transformation of a cellular host using an expression vector (plasmid, cosmid, virus, etc.) comprising the DNA sequences encoding the peptides of the invention, followed by culturing of the cellular host thus transformed, and recovery of the peptide from the culture medium. The use of vectors for the expression of proteins and peptides in the cells of host, in particular humans, is well known and will not be described in further detail.

The polypeptides and polynucleotides of the present invention can also be used to prepare polyclonal or monoclonal antibodies capable of binding (preferably specifically) to at least one polypeptide/polynucleotide which is a subject of the invention. The present invention is therefore also directed toward such purified antibodies which can be obtained by very well-known techniques such as, for example, the technique described by Kohler and Milstein (Continuous cultures of fused cells secreting antibody of predefined specificity, Nature, 1975, 262:495-497). According to a preferred embodiment of the invention, the antibodies are of the “humanized” type. Those skilled in the field, by virtue of their general knowledge, will know how to prepare these types of antibodies.

In the context of the present invention, the term “vector” refers to a polynucleotide construct designed to be transfected into various cell types. As a result, these vectors are directed toward expression vectors designed for the expression of a nucleotide sequence in a host cell; cloning vectors designed for the isolation, propagation and replication of inserted nucleotides; viral vectors designed for the production of recombinant virus or of viral particle (viral-like particle); or shuttle vectors which comprise attributes of more than one vector.

3. Methods and Process for Use

According to another aspect, the invention relates to the treatment or prevention of biochemical pathologies or mental diseases such as autism or Asperger syndrome. More particularly, the invention is directed toward the use of a nonmutated polynucleotide encoding a protein involved in synaptogenesis. Preferably, the protein consists of a cell adhesion protein, more preferably of a protein belonging to the human neuroligin family, and even more preferably the polypeptide consists of the HNL3 protein, HNL4X or the HNL4Y protein. Examples of nonmutated polynucleotides are given above.

The invention is also directed toward a method of treatment comprising the insertion into at least one portion of the cells from an affected patient of a polynucleotide encoding a polypeptide involved in synaptogenesis, such as the HNL3 or HNL4X protein. Preferably, the cells into which the polynucleotide is inserted are stem cells. Examples of satisfactory polynucleotides are given above.

According to a related aspect, the invention is directed toward a method for transforming stem cells from a patient exhibiting a mutation of a gene encoding a protein involved in synaptogenesis, the method comprising:

-   -   a) the use of stem cells from the patient;     -   b) the insertion into the genome of the stem cells, of a         polynucleotide encoding a functional polypeptide involved in         synaptogenesis, such as the HNL3 or HNL4X protein; and     -   c) the reimplantation into the patient of cells transformed         according to step b).

Those skilled in the field will be able to adapt the treatment methods mentioned above and to determine, according to several factors, the polynucleotides which should be used, the means for inserting them into the cells and the method and the amount of polynucleotides or of cells which should be administered. Among the factors which can influence their choices are: the nature of the treatment; the exact sequence of the polynucleotides; the stage of the disease; the condition, the age and the weight of the patient, etc.

According to another aspect, the invention also relates to a method for detecting biochemical disorders which alter synapse formation, stabilization and/or recognition, a predisposition to the development of psychiatric pathologies and/or a mental disease such as autism or Asperger syndrome.

Thus, the method comprises at least one of the following steps:

-   -   detecting a mutation in the sequence of a gene encoding a         protein involved in synaptogenesis, in the sequence of a         fragment of this gene or in the sequence of a messenger RNA of         this gene;     -   detecting the presence of a protein involved in synaptogenesis;     -   detecting a mutation in a protein involved in synaptogenesis;     -   measuring the biological activity of a protein involved in         synaptogenesis or its interaction with one of its protein         partners. A method for measuring such an interaction is, for         example, described in Ichtchenko et al. (J. Biol. Chem., 1996,         271(5):2676-82) or Grifman et al. (Proc.

Natl. Acad. Sci. USA, 1998, 95(23):13935-40).

According to a preferred embodiment, the method comprises:

-   -   a) amplifying a gene encoding a protein involved in         synaptogenesis, amplifying a fragment of said gene or amplifying         a messenger RNA of said gene; and     -   b) detecting a mutation in the sequence of said gene, in the         sequence of said fragment or in the sequence of said messenger         RNA.

A related aspect of the method of the invention concerns a kit (set) for detecting biochemical disorders which alter synapse formation, a predisposition to the development of psychiatric pathologies and/or a mental disease, and/or for diagnosing a mental disease. According to a preferred embodiment, the kit comprises at least one of the elements chosen from the group consisting of: a probe, an antibody, a reagent and a solid support, these elements allowing:

-   -   i) detection of a mutation in the sequence of a gene encoding a         protein involved in synaptogenesis, in the sequence of a         fragment of this gene or in the sequence of a messenger RNA of         this gene; and/or     -   ii) measurement of the biological activity of a protein involved         in synaptogenesis or of its interaction with one of its protein         partners.

Preferably, the gene to which reference is made in the method and the kit encodes, in its wild-type form, a cell adhesion protein, more preferably a protein belonging to the human neuroligin family, and even more preferably the HNL3 protein, the HNL4X protein or the HNL4Y protein.

Advantageously, the gene encodes, in its wild-type form, a protein comprising SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO:8 or SEQ ID NO:14. More preferably, the gene comprises SEQ ID NO:1 , SEQ ID NO:4 or SEQ ID NO:12.

Knowledge of the gene involved in a predisposition to the development of autism or of Asperger syndrome opens the door to the discovery of novel molecules for preventing, controlling or treating the disease. Thus, according to another aspect, the invention is directed toward a method for sorting molecules which can make it possible to modulate the biological activity of a polypeptide encoded by the polynucleotide as defined above, or the biological activity of the polypeptide as defined above. According to a preferred embodiment, the sorting method comprises:

-   -   a) bringing said polypeptide into contact with a molecule         capable of modulating its biological activity;     -   b) measuring the biological activity of said polypeptide; and     -   c) evaluating the activity measured in step b) relative to a         measurement of the biological activity of said polypeptide in         the absence of said molecule.         4. Compositions

The present invention also relates to the use of these polypeptides and of the polynucleotides encoding them, for preparing therapeutic compositions that are useful in the treatment of a mental or neurological disease, such as autism, Asperger syndrome, schizophrenia or ADHD syndrome.

In a preferred embodiment, the composition of the present invention also contains a pharmaceutically acceptable vehicle, and an element chosen from the group consisting of:

-   -   a polynucleotide according to the present invention;     -   a polypeptide according to the present invention;     -   an antibody according to the present invention;     -   a vector according to the present invention; and     -   a host cell according to the present invention.

The compositions according to the present invention can be in any solid or liquid form that is usual for pharmaceutical administration, i.e., for example, liquid administration forms or administration forms consisting of a gel, or any other support allowing, for example, controlled release. Among the compositions which can be used, mention may in particular be made of injectable compositions more particularly intended for injections into the blood circulation in humans.

Those skilled in the field will be able to prepare pharmaceutically acceptable compositions and to determine, according to several factors, the preferred mode of administration and the amount which should be administered. Among the factors which can influence their choices are: the nature of the treatment; the exact nature of the active or non-active ingredients which make up the composition; the stage of the disease; the condition, the age and the weight of the patient, etc.

The examples hereinafter will make it possible to demonstrate other characteristics and advantages of the present invention.

EXAMPLES

The examples which follow serve to illustrate the extent of the use of the present invention and not to limit its scope. Modifications and variations can be made thereto without departing from the spirit or from the scope of the invention. Although other methods or products equivalent to those which are found above may be used for testing or implementing the present invention, the preferred materials and methods are described.

Introduction

A locus for predisposition to autism has been suggested in Xp22.3 by the observation of several independent and de novo chromosomal deletions in this region. The size of the critical region deleted in these patients was approximately 10 Mb, delimited by DXYS232X (6 cM) and DXS7103 (16 cM). In support of these results, the overall analysis of the genome carried out by the Paris study (Philippe et al., 1999) indicates that the maximum LOD for the X chromosome is located in this region (11 cM).

Within this interval, we have identified the human neuroligin 4 (HNL4X) gene encoding a new member of the neuroligin family (Scheiffele et al., 2000; Song et al., 1999). These cell adhesion molecules possess a homology with acetylcholine esterases and are specifically located in the postsynaptic membrane of excitatory synapses (Song et al., 1999). They are essential factors for the formation of functional synapses since the expression of neuroligins in HeLa cells or kidney cells can trigger the development of presynaptic structures in neurons which are in contact (Scheiffele et al., 2000). We have identified five HNL genes in the human genome, located on chromosomes 3q26 (HNL1), 17p13 (HNL2), Xq13 (HNL3), Xp22.3 (HNL4X) and Yq11.2 (HNL4Y). Neuroligin phylogeny suggests that HNL3 is the common ancestor of HNL4X and HNL4Y. The expression profile for the HNLs has been determined by specific RT-PCRs in various adult (male and female) brain tissues. Expression of the HNL1-3 genes and of their alternative transcripts is found in all brain regions. HNL4X and HNL4Y are expressed at similar levels in the male brain without significant differences between the various tissues. As expected, HNL4Y is not expressed in the female brain, whereas HNL4X is expressed.

Example 1 Characterization of the HNL4X and HNL4Y Genes and Their Involvement in Psychiatric Syndromes

The phylogenetic study shows that the HATL4X genes located on the X chromosome and the HNL4Y gene located on the Y chromosome began to diverge approximately 40 million years ago, during the evolution of primates. While all the genes of the Y chromosome which diverged at this date became pseudogenes (inactive genes), HNL4Y is strongly conserved (table 1). TABLE 1 Conservation of the HNL4X and HNL4Y genes during evolution DNA Protein Compared diver- diver- sequence gence gence (nucleo- Gene pair Ks KA Ks/KA (%) (%) tides) Group 4 GYG2/GYG2P* 0.11 0.06 1.8 7 12 525 ARSD/ARSDP* 0.09 0.07 1.3 7 13 846 ARSE/ARSEP* 0.05 0.04 1.2 4 9 615 PRKX/Y 0.07 0.03 2.3 5 8 1020 HNL4X/4Y 0.079 0.012 6.456 3 2 2451 STS/STSP* 0.12 0.10 1.2 11 18 852 KAL1/KALP* 0.07 0.06 1.2 6 12 1302 AMELX/Y 0.07 0.07 1.0 7 12 576 Group 3 TB4X/Y 0.29 0.04 7.3 7 7 135 EIF1AX/Y 0.32 0.01 32 9 2 432 ZFX/Y 0.23 0.04 5.8 7 7 2394 DFFRX/Y 0.33 0.05 6.6 11 9 7671 DBX/Y 0.36 0.04 9.0 12 9 1932 CASK/CASKP* 0.24 0.22 1.1 15 32 156 UTX/Y 0.26 0.08 3.3 12 15 4068 Group 2 UBE1X/Y 0.58 0.07 8.3 16 13 693 SMCX/Y 0.52 0.08 6.5 17 15 4623 Group 1 RPS4X/Y 0.97 0.05 19 18 18 792 RBMX/Y 0.94 0.25 3.8 29 38 1188 SOX3/SRY 1.25 0.19 6.6 28 29 264 PCDHX/Y 0.006 0.008 0.809 1 2 2850

This table includes the synonymous substitution rates (KS) and nonsynonymous substitution rates (KA) of all the known genes of the X chromosome having homology on the Y chromosome. The KS/KA ratio is an indication of the gene conservation. KS is the rate of synonymous substitution per synonymous site which represents the modifications which do not change the sequence of the protein. KA is the rate of nonsynonymous substitution per nonsynonymous site which represents the modifications which change the sequence of the protein. If the KS/KA ratio=1, then the gene is not conserved since there are as many synonymous modifications as there are nonsynonmyous modifications. This is the case for the X/Y pairs having a nonfunctional pseudogene on the Y chromosome (for example, KALl/KALP*). If KS/KA >1, then the gene varies in the course of evolution but the protein is well conserved. This is the case for the HNL4/5 pair indicating that the genetic variation between these genes is subjected to a selection pressure which conserves the protein sequences of HNL4X and HNL4Y.

For the detection of mutations on the HNL4X gene, the following steps were used:

Materials and Methods

Identification of the Sequence of the HNL4X, HNL4Y and MNL4 Genes

The HNL4X and HNL4Y genes were isolated by computer analysis of the sequences of the Xp22.3 and Yq11.22 region and amplification of the complete transcripts from brain mRNA.

Computer Analysis

A systematic study of the genes of the Xp22.3 region, close to the DXS996 microsatellite, was carried out using the human genome sequencing data (http://genome.usc.edu) and http://www.ensembl.org/genomecentral). The DXS996 microsatellite is the genetic marker which shows the most significant linkage with autism in the analysis by Philippe et al. (1999, mentioned above) . We identified that this genetic marker was located in a putative gene (KIAA1260, and that a putative homolog, KIAA0951, of this gene existed, located on the Y chromosome. The partial sequence of the cDNAs of the genes encoding KIAA1260 and KIAA0951 was deduced from the genomic sequence. A (BLAST) sequence alignment analysis and a phylogenetic tree grouping together the other human neuroligins were effected so as to define that KIAA1260 and KIAA0951 are new members of the neuroligin family which we henceforth call HNL4X and HNL4Y.

Analysis of the HNL4X and HNL4Y Transcripts

Total RNA from human brains coming from various men (n=5) and women (n=5) was isolated from biopsies of frontal cortex. The complete cDNAs of the HNL4X and HNL4Y mRNAs were reverse transcribed, amplified and directly sequenced. The oligonucleotides used for the amplification and sequencing are indicated in tables 2 and 3.

Sequencing of the HNL4X and HNL4Y Genes in Autistic and Asperger Individuals

Each exon of the HNL4X and HNL4Y genes was amplified and sequenced from the genomic DNA. The name and the sequence of each primer are indicated in table 3. TABLE 2 Names and sequences of the primers used to amplify and sequence the HNL4X and HNL4Y cDNAs Exons HNLXY1 ACCCCGCGTGAAGATGAAATG SEQ ID NO:18 1-6 HNLXYE6dR GAGGGATAGGARGGGAAATAG SEQ ID NO:19 Exons HNLXYE2F GGATGTGGATGCAGATTTGAA SEQ ID NO:20 2-5 HNLXY4 GCTCTGAATGATGGCCTTCTG SEQ ID NO:21 Exons HNLXY10 TCCTGGATCAGATTCAAGCAC SEQ ID NO:22 4-6 HNLXYE6dR GAGGGATAGGARGGGAAATAG SEQ ID NO:23 Exons HNLXYE2F GGATGTGGATGCAGATTTGAA SEQ ID NQ:24 2-6 HNLXYE6dR GAGGGATAGGARGGGAAATAG SEQ ID NO:25

For the degenerate primers, use of the universal code: M(AC), R(AG), W(AT), S(CG), Y(CT), K(GT), V(ACG), H(ACT), D(AGT), B(CGT), N(ACGT) TABLE 3 Names and sequences of the primers used to sequence the HNL4X and HNL4Y genes SEQ ID Exons Primers Sequences NO: Exon 1a HNLXYE1aF GAAACAACGAATTTCCTCCAAA 26 HNL4X HNLXYE1aR AGTGAGGCTTTCCATCCTTTGC 27 Exon 1b HNLXE1F ATTCTTTAAGAAAACTGTCAGC 28 HNL4X HNLXYE1R CACGGGAAAGGGGTGCATGGA 29 Exon 1 HNLYE1F GGGGTGCTTCTTTTGGGAGGCT 30 HNL4Y HNLXYE1R CACGGGAAAGGGGTGCATGGA 31 Exon 2 HNLXYE2F GGATGTGGATGCAGATTTGAA 32 HNLX/Y HNLXE2Rbis GTATTGTTTTCTGTTCCAGTG 33 Exon 3 HNLXYE3F TGTGTTTCCGTACTTGGCTTT 34 HNL4X/Y HNLXYE3R GCTTAGTCATTCACATGATGAA 35 Exon 4 HNLXYE4F ACCAAAAATCTCTTGTGTTCT 36 HNL4x HNLXYE4R TTCTTGGTTCAGGGTATTTGC 37 Exon 4 HNLYE4F AACAAAAATGTCCTGTGTTCT 38 HNL4Y HNLXYE4R TTCTTGGTTCAGGGTATTTGC 39 Exon 5 RNLXYE5dF TGTCCRCAATTTTGCACCTGC 40 HNL4X/Y HNLXYE5dR AGGAYAGTGATACCCCAACA 41 Exon 6 HNLXYE6Fbis AGAGCAGATTGTAACTTCCTG 42 RNL4X/Y HNLXYE6dR GAGGGATAGGARGGGAAATAG 43

For the degenerate primers, use of the universal code: M(AC), R(AG), W(AT), S(CG), Y(CT), K(GT), V(ACG), H(ACT), D(AGT), B(CGT), N(ACGT). TABLE 4 Names and sequences of the primers used for the amplification of the MNL4 cDNA (57BL6 mouse) Primer Sequence SEQ ID NO: MNL4F8 CGTGACGAAACAGGAAGTGACC 44 MNL4R8 GTAGCCAAGGCCCCTGCATGTC 45

TABLE 5 Names and sequences of the primers used for the amplification of MNL4 in three PCRs of approximately 1 kb Primer Sequence SEQ ID NO: MNL4F8 CGTGACGAAACAGGAAGTGACC 46 MNL4R2 AGCCGAAGACGGTGACGCGGTC 47 MNL4F12 AGGAAGCCGGTCATGGTTTACA 48 MNL4R5 ACGCTCAGCTCCGTCGAGTAGT 49 MNL4F14 AGACGCTCGTGGCGCTCTTCAC 50 MNL4R8 GTAGCCAAGGCCCCTGCATGTC 51

TABLE 6 Names and sequences of the primers used for the amplification of HNL3 PRIMER SEQUENCE SEQ ID NO: RNL3E2F CCTATTGGGCTGATGCTGTGACC 52 HNL3E2R AGGGCACACAACCACATGCAAG 53 HNL3E3Fbis TTGAGCTCCAGGTTGAGCAACC 54 HNL3E3RBIS CCCCTTGCGAAGCCAGTCTTCC 55 HNL3E4F CTGCGTGCTCATTCTCTATTCC 56 HNL3E4R GTAGAAGAGAGCTGGCCGATTC 57 HNL3E5F ATGGCTATGTGTGACACGACAG 58 HNL3E5R GGAAGATGAGTGAAGGGGTACC 59 HNL3EGF TTTCCTCATCCAGATAGAGTGG 60 HNL3E6R CATGTGTTCCTGGATCTGGGAG 61

In order to test this gene in autistic individuals, the genomic structure of the various HNLs was defined and the coding portions (Exon 2-Exon 6) were amplified. Thus, 140 autistic boys and 18 autistic girls were tested for most of the HNL4X/4Y coding portion.

In a Swedish family with two affected brothers, one with autism and the other exhibiting Asperger syndrome, an additional thymidine was identified at nucleotide 1186 of the HNL4X gene, creating a stop codon (FIG. 17). This mutation (D396stop) is located in the esterase domain, producing a premature termination of the protein and deleting the transmembrane domain. This change is inherited from the mother, but is absent in the maternal grandmother, in the two maternal aunts and in the unaffected child, indicating the de novo status of this mutation in the mother of the affected boys. In addition, this mutation was not found in 350 controls (250 women and 100 men).

In addition, the boy/girl ratio, which is four for autism and nine for Asperger syndrome, corroborates this observation according to which HNL4X/4Y influences synaptogenesis and the mutation of HNL4X/4Y constitutes a factor for predisposition to mental diseases, in particular autism and Asperger syndrome.

The identification of this stop mutation in a primate-specific gene carried by the X chromosome in two autistic individuals, and involved in synaptogenesis, is one of the first functional mutations identified in a psychiatric disease. This mutation is also the first mutation described which is associated with autism without any other clinical sign (fragile X, tubercular sclerosis, etc.).

Example 2 Characterization of the HNL3 Gene and of its Involvement in Psychiatric Syndromes

During the search for mutations in HNL3, the ancestral gene for HNL4X/Y located in the Xq13 region, in two independent families, two amino acid changes located in highly conserved regions of the protein were identified. One of the two families is very similar to the first family mutated in HNL4X. The two affected brothers, the first affected with autism and the second with Asperger syndrome, received the mutation from their mother. Interestingly, the mother also has a brother with Asperger syndrome and other relatives with psychiatric disorders. The mutation (R451C) is located in the esterase domain of the protein and concerns an amino acid that is conserved during evolution since it is present in all neuroligins (including in D. melanogaster) and in all the mammalian, fish, reptile and bird acetylcholine esterases sequenced to date (see FIG. 6). The mutation is absent in 200 controls (100 women and 100 men). These results support the role of neuroligins in the etiology of mental disorders or psychiatric diseases such as autism and Asperger syndrome. MNL4, the orthologs of HNL4X in mice, was also identified. This new gene should make it possible to understand the deficiency induced by a mutation such as the HNL4X mutation in autism (see FIG. 19).

The final examination of the genome carried out on Finnish families with members suffering from autism (Auranen, et al., 2002) identified two very significant linkage peaks at 3q26 (exactly where HNL1 is located) and at Xq13-21 (exactly where HNL3 is located). The Xp22.3 region, containing HNL4X, is also deleted in two patients with schizophrenia. It is therefore possible that neuroligins are also responsible for susceptibility to this syndrome (schizophrenia affects 1% of the population). 

1. An isolated or purified polynucleotide encoding a polypeptide involved, in its wild-type form, in synaptogenesis, characterized in that at least one mutation in the nucleic acid sequence of said polynucleotide is associated with the development of neurological diseases and/or with a predisposition to the development of mental disorders or psychiatric diseases.
 2. The polynucleotide as claimed in claim 1, characterized in that said protein is a cell adhesion protein.
 3. The polynucleotide as claimed in claim 2, characterized in that said protein belongs to the human neuroligin family.
 4. The polynucleotide as claimed in any one of claims 1 to 3, characterized in that it is mutated so as to encode a nonfunctional mutated protein.
 5. The polynucleotide as claimed in claim 4, characterized in that said protein is HNL3.
 6. The polynucleotide as claimed in claim 5, characterized in that it encodes a protein comprising a sequence chosen from the group consisting of: SEQ ID NO:10, SEQ ID NO:11 and the fragments of this protein.
 7. The polynucleotide as claimed in claim 5 or 6, characterized in that it comprises SEQ ID NO:13 and the sequences of at least 20 consecutive nucleotides derived from said sequence.
 8. The polynucleotide as claimed in any one of claims 1 to 4, characterized in that said protein is HNL4X or HNL4Y.
 9. The polynucleotide as claimed in claim 8, characterized in that it encodes a protein comprising a sequence chosen from the group consisting. of: SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO:8 and the fragments of this protein.
 10. The polynucleotide as claimed in claim 8 or 9, characterized in that it comprises a sequence chosen from the group. consisting of: SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:.4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:16, SEQ ID NO:17 and the sequences of at least 20 consecutive nucleotides derived from said sequences.
 11. The polynucleotide as claimed in any one of claims 8 to 10, characterized in that the protein is HNL4X, and in that said polynucleotide is mutated in such a way that said mutation causes early termination of the protein.
 12. The polynucleotide as claimed in claim 11, characterized in that it comprises SEQ ID NO:1, and in that said mutation is an insertion of a thymine at position 1186, from position 465 of FIG.
 9. 13. The polynucleotide as claimed in any one of claims 8 to 12, characterized in that said mutation causes the production of a defective protein lacking its transmembrane portion.
 14. The polynucleotide as claimed in any one of claims 1 to 13, characterized in that said mutation is associated with a predisposition to the development of autism, of Asperger syndrome, of schizophrenia or of ADHD syndrome.
 15. An isolated or purified polypeptide, characterized in that it encodes a polynucleotide as claimed in any one of claims 1 to
 14. 16. An isolated or purified polypeptide, characterized in that it is involved in synaptogenesis, and in that the presence of at least one mutation in the amino acid sequence of said polypeptide is associated with a predisposition to the development of mental disorders or psychiatric diseases.
 17. The polypeptide as claimed in claim 15 or 16, characterized in that it consists of a cell adhesion protein.
 18. The polypeptide as claimed in any one of claims 15 to 17, characterized in that it consists of a protein belonging to the human neuroligin family.
 19. The polypeptide as claimed in claim 18, characterized in that it is mutated and nonfunctional.
 20. The polypeptide as claimed in claim 19, characterized in that it consists of the HNL3 protein.
 21. The polypeptide as claimed in claim 20, characterized in that it comprises a sequence chosen from the group consisting of: SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:15 and the sequences of at least 20 consecutive amino acids of SEQ ID NO:10, of SEQ ID NO:11 or of SEQ ID NO:15.
 22. The polypeptide as claimed in claim 21, characterized in that said mutation causes an amino acid substitution at position 451 or 796 of FIG.
 18. 23. The polypeptide as claimed in claim 22, characterized in that said mutation at position 451 is a substitution of an arginine with a cysteine.
 24. The polypeptide as claimed in claim 22, characterized in that said mutation at position 796 is a substitution of an asparagine with a serine.
 25. The polypeptide as claimed in any one of claims 15 to 18, characterized in that it consists of the HNL4X protein or the HNL4Y protein.
 26. The polypeptide as claimed in claim 25, characterized in that it comprises a sequence chosen from the group consisting of: SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO:8 and the sequences of at least 20 consecutive amino acids of SEQ ID NO: 3, of SEQ ID NO: 6 or of SEQ ID NO:8.
 27. The polypeptide as claimed in claim 25 or 26, characterized in that said mutation causes early termination of said protein.
 28. The polypeptide as claimed in any one of claims 25 to 27, characterized in that said mutation engenders a protein lacking its transmembrane portion.
 29. The polypeptide as claimed in any one of claims 25 to 28, characterized in that said mutation causes a D396stop termination of the protein.
 30. The polypeptide as claimed in any one of claims 12 to 29, characterized in that said mutation is associated with a predisposition to the development of autism, of Asperger syndrome, of schizophrenia or of ADHD syndrome.
 31. A method for detecting biochemical disorders which alter synapse formation, and/or a predisposition to the development of psychiatric pathologies and/or a mental disease, comprising at least one of the following steps: detecting a mutation in the sequence of a polynucleotide as defined in claim 1, in the sequence of a fragment of said polynucleotide or in the sequence of a messenger RNA of said polynucleotide; detecting the presence of a polypeptide as defined in claim 16; detecting a mutation in the polypeptide as defined in claim 16; measuring the activity of a polypeptide as defined in claim 16, or the interaction of said polypeptide with one of its protein partners.
 32. The method as claimed in claim 31, comprising: amplifying a gene encoding, in its wild-type (nonmutated) form, a protein involved in synaptogenesis, amplifying a fragment of said gene or amplifying a messenger RNA of said gene; detecting a mutation in the sequence of said gene, in the sequence of said fragment or in the sequence of said messenger RNA.
 33. The method as claimed in claim 31 or 32, characterized in that the gene encodes, in its wild-type form, a cell adhesion protein.
 34. The method as claimed in any one of claims 31 to 33, characterized in that said protein belongs to the human neuroligin family.
 35. The method as claimed in any one of claims 31 to 34, characterized in that said protein is HNL3.
 36. The method as claimed in any one of claims 31 to 35, characterized in that said gene encodes, in its wild-type form, a protein comprising SEQ ID NO:14.
 37. The method as claimed in any one of claims 30 to 35, characterized in that said gene comprises SEQ ID NO:
 12. 38. The method as claimed in any one of claims 30 to 37, characterized in that said mutation causes an amino acid substitution at position 451 or 796 of FIG.
 18. 39. The method as claimed in claim 38, characterized in that said mutation at position 451 is a substitution of an arginine with a cysteine.
 40. The method as claimed in claim 38, characterized in that said mutation at position 796 is a substitution of an asparagine with a serine.
 41. The method as claimed in any one of claims 31 to 34, characterized in that said protein is HNL4X or HNL4Y.
 42. The method as claimed in claim 41, characterized in that said gene encodes, in its wild-type form, a protein comprising SEQ ID NO:3, SEQ ID NO:6 or SEQ ID NO:8.
 43. The method as claimed in claim 41 or 42, characterized in that said gene comprises SEQ ID NO:1 or SEQ ID NO:4.
 44. The method as claimed in any one of claims 41 to 43, characterized in that said protein is HNL4X, and in that said mutation causes early termination of the protein.
 45. The method as claimed in claim 44, characterized in that said mutation causes the production of said protein lacking its transmembrane portion.
 46. The method as claimed in any one of claims 41 to 45, characterized in that said gene consists of SEQ ID NO:1, and in that said mutation is an insertion of a thymine at position 1186, from position 465 of FIG.
 9. 47. The method as claimed in any one of claims 31 to 46, characterized in that the disorder or the mental disease consists of autism, Asperger syndrome, schizophrenia or ADHD syndrome.
 48. A kit for detecting biochemical disorders which alter synapse formation, and/or a predisposition to the development of psychiatric pathologies and/or a mental disease, and/or for diagnosing a mental disease, the kit comprising at least one of the elements chosen from the group consisting of: a probe, an antibody, a reagent and a solid support for: i) detecting a mutation in the sequence of a polynucleotide as defined in claim 1, in the sequence of a fragment of said polynucleotide or in the sequence of a messenger RNA of said polynucleotide; and/or ii) measuring the biological activity of a polypeptide as defined in claim 16 or the interaction of said polypeptide with one of its protein partners.
 49. Kit as claimed in claim 48, characterized in that said gene encodes a protein comprising SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO:8 or SEQ ID NO:14.
 50. The kit as claimed in claim 48 or 49, characterized in that said gene comprises SEQ ID NO:1, SEQ ID NO:4, SEQ ID NO: 12, SEQ. ID NO: 16 or SEQ ID NO:17.
 51. The kit as claimed in any one of claims 48 to 50, characterized in that said protein comprises a sequence chosen from the group consisting of: SEQ ID NO:3, SEQ ID NO:6, SEQ ID NO 8 and SEQ ID NO:14.
 52. The use of a nonmutated polynucleotide encoding a protein involved, in its wild-type form, in synaptogenesis, for treating or preventing biochemical pathologies or mental diseases.
 53. The use of a nonmutated protein which is involved, in its wild-type form, in synaptogenesis, for treating or preventing biochemical pathologies or mental diseases.
 54. The use as claimed in claim 52 or 53, characterized in that said protein is a cell adhesion protein.
 55. The use as claimed in any one of claims 52 to 54, characterized in that said protein belongs to the human neuroligin family.
 56. The use as claimed in any one of claims 52 to 55, characterized in that said protein is HNL3 or HNL4X.
 57. The use as claimed in any one of claims 52 to 56, characterized in that said mental disease is autism, Asperger syndrome, schizophrenia or ADHD syndrome.
 58. A method for sorting molecules which makes it possible to modulate the biological activity of the polypeptide encoded by the polynucleotide as claimed in one of claims 1 to 14 or the biological activity of the polypeptide as claimed in one of claims 15 to 29, comprising: a) bringing said polypeptide or a recombinant cell containing it into contact with a molecule capable of modulating its biological activity; b) measuring the biological activity of said polypeptide or measuring the interaction of said polypeptide with one of its protein partners; and c) evaluating the activity measured in step b), relative to a measurement of the biological activity of said polypeptide in the absence of said molecule.
 59. A method for treating a mental or neurological disease, comprising the insertion into at least one portion of the cells from an affected patient of a polynucleotide encoding a polypeptide as defined in claim
 16. 60. The method as claimed in claim 59, characterized in that said cells are stem cells.
 61. The method as claimed in claim 59 or 60, characterized in that said mental disease is autism, Asperger syndrome, schizophrenia or ADHD syndrome.
 62. The method as claimed in any one of claims 59 to 61, characterized in that a gene encoding a functional HNL3 protein and/or encoding a functional HNL4X protein is inserted.
 63. The method as claimed in claim 62, characterized in that the HNL3 protein possesses SEQ ID NO:14.
 64. The method as claimed in claim 62, characterized in that the HNL4X protein possesses SEQ ID NO:3.
 65. A method for transforming stem cells from a patient exhibiting a mutation of a gene encoding a protein involved in synaptogenesis, characterized by: a) the use of stem cells from said patient; b) the insertion into the genome of said stem cells of a polynucleotide as defined in claim 1; and c) the reimplantation into the patient of cells transformed according to step b).
 66. A purified monoclonal or polyclonal antibody which recognizes specifically at least one of the polynucleotides defined in claims 1 to 14 and/or at least one of the polypeptides defined in claims 15 to
 30. 67. The antibody as claimed in claim 66, characterized in that it is humanized.
 68. A cloning or expression vector comprising one of the polynucleotides defined in claims 1 to 14 or a fragment thereof.
 69. A vector as claimed in claim 68, characterized in that said vector is chosen from plasmids, cosmids and phages.
 70. A host cell comprising a polynucleotide as claimed in any one of claims 1 to 14 and/or a vector as claimed in claim 68 or
 69. 71. A composition, characterized in that it also contains a pharmaceutically acceptable vehicle, and at least one element chosen from the group consisting of: a polynucleotide as claimed in any one of claims 1 to 14; a polypeptide as claimed in any one of claims 15 to 30; an antibody as claimed in claim 66 or 67; a vector as claimed in claim 68 or 69; and a host cell as claimed in claim
 70. 